An apparatus for use with electronic and/or mechanical access control devices includes a holder which receives a removable insert which may include an electronic module with a cover member securing the insert to the holder. The holder may take various forms and may be in the form of a key ring,...http://www.google.de/patents/US5775148?utm_source=gb-gplus-sharePatent US5775148 - Universal apparatus for use with electronic and/or mechanical access control devices 
